Ji Lei, Jia Yongfeng, Wang Xia, Duan Limei, Li Weishan, Liu Jinghai, Zhang Yuegang
Inner Mongolia Key Laboratory of Carbon Nanomaterials, Nano Innovation Institute (NII), College of Chemistry and Materials Science, Inner Mongolia University for Nationalities, Tongliao, 028000, People's Republic of China.
School of Chemistry, South China Normal University, Guangzhou, 510000, People's Republic of China.
Nanotechnology. 2021 May 7;32(19):192002. doi: 10.1088/1361-6528/abe002.
Lithium/sulfur (Li/S) batteries have emerged as one of the most promising next-generation energy storage systems with advantages of high theoretical energy density, low cost and environmental friendliness. However, problems regarding to severe shuttle effect of soluble polysulfide, poor electronic/ionic conductor of solid charged/discharged products (S and LiS), and fatal swell of volume along with the growth of Li dendrites greatly deteriorate the sulfur utilization and capacity retention during extended charge-discharge cycles. With advantages of high nitrogen content, lithiophilic modulation and tunable charge density and charge transfer, carbon nitride (g-CN) has played a positive role in restricting the shuttle effects and dendrite formation. This minireview mainly discusses these research achievements of g-CN in Li/S batteries, aiming to provide a basic understanding and direct guidance for further research and development of functionalized g-CN materials in electrical energy storage. The two-dimensional (2D) structure of g-CN with abundant hierarchical pores improves its accommodation capacity for sulfur by effectively confining the lithium polysulfides (LiPSs) into the pores, and provides favorable channels for ion diffusion. The rich nitrogen and carbon defects further offer more active sites for strongly adsorbing LiPSs and bridge electron transfer pathway at atomic scale for catalytic reactions to accelerate redox kinetics of Li/S conversion chemistry. Moreover, the features of lithiophilic wettability, high adsorption energy and densely distributed lithiophilic N of g-CN provide a large number of adhesive sites for lithium cation (Li) and disperse the nucleation sites to enable uniform nucleation and deposition of Li on the anode surface and to suppress formation and growth of Li dendrites. Finally, the g-CN also effectively regulates the wettability between Li anode and solid inorganic electrolyte, and reduces the crystallinity of solid polymer electrolyte to enhance the Li migration ability and ionic conductivity.
锂硫（Li/S）电池已成为最具潜力的下一代储能系统之一，具有高理论能量密度、低成本和环境友好等优点。然而，可溶性多硫化物的严重穿梭效应、固体充放电产物（S和LiS）的电子/离子传导性差以及随着锂枝晶生长而出现的致命体积膨胀等问题，极大地降低了在长时间充放电循环过程中的硫利用率和容量保持率。氮化碳（g-CN）具有高氮含量、亲锂调制以及可调节的电荷密度和电荷转移等优点，在限制穿梭效应和枝晶形成方面发挥了积极作用。本综述主要讨论g-CN在Li/S电池中的这些研究成果，旨在为储能领域功能化g-CN材料的进一步研发提供基本认识和直接指导。g-CN的二维（2D）结构具有丰富的分级孔隙，通过有效地将多硫化锂（LiPSs）限制在孔隙中提高了其对硫的容纳能力，并为离子扩散提供了有利通道。丰富的氮和碳缺陷进一步提供了更多的活性位点，用于强烈吸附LiPSs，并在原子尺度上搭建电子转移途径以加速Li/S转化化学的氧化还原动力学催化反应。此外，g-CN的亲锂润湿性、高吸附能和密集分布的亲锂N特性为锂阳离子（Li）提供了大量的粘附位点，并分散了成核位点，使Li能够在阳极表面均匀成核和沉积，从而抑制Li枝晶的形成和生长。最后，g-CN还有效地调节了锂阳极与固体无机电解质之间的润湿性，并降低了固体聚合物电解质的结晶度，以增强Li的迁移能力和离子电导率。
